1. Field of the Invention
The present invention relates to devices for inducing hypothermia.
2. Description of the Related Art
Induced therapeutic hypothermia and other medically-induced cooling methods are promising treatments with wide-ranging applications. The reduction of patients' body temperature during strokes, heart attacks and brain or spine injuries has been shown to reduce secondary complications caused by ischemia and other impairments to oxygen and blood flow. Induction of mild hypothermia has been hypothesized to significantly decrease intracranial pressure and secondary neurological injury. The Hypothermia after Cardiac Arrest Study Group. “Mild Therapeutic Hypothermia to Improve the Neurologic Outcome after Cardiac Arrest.” New England Journal of Medicine 346.8 (2002): 549-56.
Hypothermia can be applied in many circumstances, including in emergency settings to mitigate damage, and during surgeries to reduce the risk of ischemia. Currently known methods of induced hypothermia include external cooling baths and blankets, and internal circulation of fluids and gasses, whether directly into the body or within delivery means such as balloon catheters. Many methods are aimed at inducing systemic hypothermia, i.e. hypothermia induced to the whole body. In fact, induction of systemic hypothermia is now the standard of care in the management of patients who survive cardiac arrest.
More specific applications of applied cooling methods include, but are not limited to, pain relief, prevention of chemotherapy induced hair loss, and reduction of discomfort of braces and casts. In addition, some devices seek to induce systemic hypothermia using localized techniques, because systemic hypothermia is associated with a host of negative side effects such as bleeding diathesis, shivering, arrhythmias, suppression of the immune system, and electrolyte imbalance. Some such devices focus on cooling the brain, for instance using cooling helmets. Others purport to deliver cooling directly to circulating fluids, for instance, the bloodstream (see U.S. Pub. No. 2002/0030717 A1), or cerebrospinal fluid (see U.S. Pat. No. 2007/0005121 A1). Inserts such as catheters are cooled using the circulation of fluid to the inserted device. These devices, however, are limited by the freezing point of the fluid, and they can rupture or leak fluid, resulting in dangerous contamination. Furthermore, balloon catheter use has been associated with increased risk of deep vein thrombosis (DVT) and clotting.